In late January, Bill Gates expertly trolled the 10-year challenge meme with a tweet that said: "It’s hard to beat this #10YearChallenge." The tweet included a graphic that showed how, in the last 10 years, extreme poverty, child mortality and youth illiteracy were all way down, while life expectancy was up.

The Gates' optimism is delightful. But it's easy to shrug it off as the rose-tinted perspective of a couple luxuriating in an abundance of gifts: intelligence, love, family, success and more money than King Midas.

I recently spent the day at the Bill & Melinda Gates Foundation, walking a mile in the billionaires' shoes, so to speak, and talking with some of the managers and directors who run various programs there.

Hearing about their work was inspiring and gave me a newfound hope for the future, just like Bill's.

And the reason is simple. These people are taking on some of the world's hairiest, most complex and seemingly intractable problems.

And they are winning.

Death to polio and malaria

Gates' father, Bill Gates, Sr., was the first to run the family charitable foundation in the late '90s. The foundation has morphed into a much bigger entity over time, especially after it became the main focus of Bill and Melinda Gates themselves.

Brian Ach/Getty ImagesThe elder Bill Gates' presence still hangs large at the Foundation's visitor's center, which is a cross between a techie interactive kids' museum, a community educational facility, and a place to learn about the Foundation's work.

A video of Gates' dad introduces himself, and explains that because of the "other fellow" — that is, his famous son — he's known as "Senior."

In its early days, the foundation focused mostly on local charity, but turned its attention to global health after Bill Gates Jr. read an article on children in poor countries dying from preventable illnesses.

He sent the article to his dad with a note that said: "Dad, maybe we can do something about this."

Those words are now plastered in giant letters in the visitor's center.

The foundation has since become a major force in global health. It joined a global effort to eradicate polio in 2007. In 1988 there were an estimated 350,000 case of polio worldwide. In, 2018, there were only 29 reported cases.

Business Insider/Julie Bort

Gunning for malaria

The success with polio is a source of pride and inspiration at the foundation. To them, it's proof that hard problems like distributing vaccines to poor, remote children can be solved by smart people and repeatable systems.

With Bill and Melinda as their leaders, the people at the foundation are stunningly smart with impressive credentials: I met neuroscientists, biologists and infectious disease specialists.

With polio almost over, the foundation now wants to end malaria.

Business Insider/Julie BortLike the others I met, Philip Welkhoff, the director of the Malaria team, has a personal interest in the mission — and impressive credentials. He grew up in Haiti and had malaria himself as a kid. He became a rocket scientist, then earned his PhD in computational neuroscience from Princeton and turned his attention to global health.

He loves his job because he's saving lives.

"All the work that the international community does together saves about 500,000 people from malaria every year compared to the early 2000s. That's a half million lives every single year," he told me.

The current challenge is to reach the most remote locations, which the foundation has expertise in doing, and containing outbreaks. No malaria vaccine is rolled out yet, but the foundation is having a lot luck by increasing the distribution of mosquito-killing bed nets.

But even a limited outbreak can turn into a bigger infection once mosquitoes start transmitting the illness, and people move from place to place. And so, malaria is even more complicated to eradicate than polio.

Still, there's steady progress, and the goal is to reduce malaria deaths 90% by 2030 compared to their 2015 level.

The toilet team

Outside of malaria, one of the projects that gets a lot of attention is Bill Gates' off-the-grid toilet project, which asks scientists to rethink the toilet.

Gates launched the Reinvent the Toilet challenge in 2011, asking researchers to come up with toilets that could sanitize human waste with no water, electricity, sewer or septic system. The toilets were to clean the waste and reclaim the water to safe drinking water standards, as well as to harvest other nutrients for other uses, a game-changer to those living without sanitation.

Some of those original teams went to the nines on their designs. One team even held a "smell summit" working with perfume makers who recreated latrine smells. This to help them test their methods for countering such smells. That work involving taking whiffs of those lovely scents.

The director of the toilet project is Brian Arbogast — though his real title is "director, Water, Sanitation, and Hygiene," and his job involves more than just toilets. He's funding a variety of projects that improve human sanitation.

Business Insider/Julie BortArbogast was an early Microsoft employee, spending 22 years rising to the level of corporate vice president. He left the company to become a cleantech investor, and has been on the boards of various clean-water entities and charities. He worked closely with Bill Gates for decades before joining the foundation in 2013.

When the toilet project was first started, no one knew if it could really be done, Arbogast said. In 2015, though, one inventor produced a system called the Omni Processor. It's not a toilet, but an off-grid fecal sludge treatment plant that outputs purified water. One day it may also output electricity.

A working prototype has been operating in Dakar, Senegal in Africa for a few years. Arbogast believes the tech will eventually influence sanitation in the developed world, including green buildings, septic systems and remote, off-the-grid cabins.

The latest version has been licensed to three commercial companies: the US company created by the tech's inventor, Sedron Technologies, as well as a company in China and one in India.

YouTube/GatesNotes

Poop hats and toilet water

Bill Gates famously drank the sewage water produced from the Dakar Omni Processor in 2015. And there are lots of stories at the foundation and in the Gates household about that water.

"Two weeks before [Bill drank], I had to drink from it, as did most of the team," Arbogast told us.

Melinda Gates told us that her daughter made her drink that water, too. Bill Gates drove around with a 2-liter bottle of it in his car for weeks, and every time someone got in the car, their daughter made them drink some.

"If we got sick — which we didn’t — it would not have not been from the water, but because we’re all passing it around," Melinda Gates laughed.

Gates spread the love around, too: In 2015, he tricked Jimmy Fallon into drinking that water on the air, as well.

And there are actual toilets in development, too, with models on display (but not available for use) at the foundation's visitor's center.

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In November, Arbogast's team and Bill Gates spearheaded the Reinvented Toilet expo in Beijing. It drew in 1,200 attendees, and loads of exhibitions for new sanitation tech.

The group wears their association with poop as a badge of honor, Arbogast says.

He keeps a hat that looks like a poop emoji in his office, and someone on his team often gets to wear it like a crown.

"The poop hat gets passed on for a job well done," he said.

Worldwide clout

Dr. Kathy Kahn is a scientist who funds agricultural projects. Kahn is having success with projects that improve how plants do photosynthesis. These plants grow faster using far less water. It's a promising field for arid countries, as well as for growing food adapted to climate change.

Kahn came to the foundation after working at the U.S. Department of Agriculture. She said one of the things that makes her work here different is the foundation's name recognition.

While other nonprofits toil in obscurity, the Gates Foundation carries prestige. She gets a seat at the table with worldwide policy makers and the top scientists in her field. It's a scientist's dream, she says.

In awe of the Gates'

One of the themes we heard repeatedly was how much employees appreciated their access to Bill and Melinda Gates. They are heavily involved, eagle-eyed, ask penetrating questions and they work as a team, each bringing different perspectives.

Elaine Thompson/AP ImagesProgress meetings with them can feel exhilarating and nervewracking, like any employee feels about presenting to their CEO.

But there's a general sense of good humor, too.

If a technical issue occurs, say with the videoconferencing system, and an employee can't immediately fix it, Bill Gates can do it without blinking an eye. There's nothing like having one of the fathers of the PC industry in the room when tech support is needed.

Another theme was just about the thrill of having Bill or Melinda Gates get excited about the employee's projects or work.

Helping whole countries get healthier

Of all the stories, Dr. Jean Kagubare's was one of the most moving.

Born in Rwanda, his parents fled the country when he was a baby. He became a doctor and returned to Rwanda right after the genocide of the 1990s. He ran several national health programs and one the country's biggest hospitals before moving to the US and getting his PhD in health systems at John Hopkins. He stayed in the US, working in global health, landing at the foundation about two years ago.

Business Insider/Julie BortHis job is to coordinate resources and measure results to ensure the healthcare system is improving. For instance, the foundation has funded a telemedicine app that helps doctors treat far-flung patients in villages without forcing them to travel to a healthcare facility.

Prior to this program, global healthcare workers would sort of parachute in to a country and focus on their one area — distributing vaccines or providing prenatal care, he explained. Those programs still exist, but now they are coordinated in a more holistic way, and his program measures total healthcare improvement, rather than just progress in one area.

"Bill Gates asks the question all time: Is our money going to where it should be? Are the right people getting help?" he said.

All of this means that Kagubare is helping far more people across the globe, and especially in his home country, than he could when he worked as a doctor.

"I was in Rwanda two months ago and talked to people and patients there. Patients are getting treatment that costs less and they don’t have wait four hours at facilities, the average wait time, or pay to go to [far away] clinics," he said.